/**
 * Copyright (c) 2014 Petka Antonov
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:</p>
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 * 
 */
"use strict";
function arrayCopy(src, srcIndex, dst, dstIndex, len) {
    for (var j = 0; j < len; ++j) {
        dst[j + dstIndex] = src[j + srcIndex];
    }
}

function pow2AtLeast(n) {
    n = n >>> 0;
    n = n - 1;
    n = n | (n >> 1);
    n = n | (n >> 2);
    n = n | (n >> 4);
    n = n | (n >> 8);
    n = n | (n >> 16);
    return n + 1;
}

function getCapacity(capacity) {
    if (typeof capacity !== "number") return 16;
    return pow2AtLeast(
        Math.min(
            Math.max(16, capacity), 1073741824)
   );
}

function Queue(capacity) {
    this._capacity = getCapacity(capacity);
    this._length = 0;
    this._front = 0;
    this._makeCapacity();
}

Queue.prototype._willBeOverCapacity =
function Queue$_willBeOverCapacity(size) {
    return this._capacity < size;
};

Queue.prototype._pushOne = function Queue$_pushOne(arg) {
    var length = this.length();
    this._checkCapacity(length + 1);
    var i = (this._front + length) & (this._capacity - 1);
    this[i] = arg;
    this._length = length + 1;
};

Queue.prototype.push = function Queue$push(fn, receiver, arg) {
    var length = this.length() + 3;
    if (this._willBeOverCapacity(length)) {
        this._pushOne(fn);
        this._pushOne(receiver);
        this._pushOne(arg);
        return;
    }
    var j = this._front + length - 3;
    this._checkCapacity(length);
    var wrapMask = this._capacity - 1;
    this[(j + 0) & wrapMask] = fn;
    this[(j + 1) & wrapMask] = receiver;
    this[(j + 2) & wrapMask] = arg;
    this._length = length;
};

Queue.prototype.shift = function Queue$shift() {
    var front = this._front,
        ret = this[front];

    this[front] = void 0;
    this._front = (front + 1) & (this._capacity - 1);
    this._length--;
    return ret;
};

Queue.prototype.length = function Queue$length() {
    return this._length;
};

Queue.prototype._makeCapacity = function Queue$_makeCapacity() {
    var len = this._capacity;
    for (var i = 0; i < len; ++i) {
        this[i] = void 0;
    }
};

Queue.prototype._checkCapacity = function Queue$_checkCapacity(size) {
    if (this._capacity < size) {
        this._resizeTo(this._capacity << 3);
    }
};

Queue.prototype._resizeTo = function Queue$_resizeTo(capacity) {
    var oldFront = this._front;
    var oldCapacity = this._capacity;
    var oldQueue = new Array(oldCapacity);
    var length = this.length();

    arrayCopy(this, 0, oldQueue, 0, oldCapacity);
    this._capacity = capacity;
    this._makeCapacity();
    this._front = 0;
    if (oldFront + length <= oldCapacity) {
        arrayCopy(oldQueue, oldFront, this, 0, length);
    }
    else {        var lengthBeforeWrapping =
            length - ((oldFront + length) & (oldCapacity - 1));

        arrayCopy(oldQueue, oldFront, this, 0, lengthBeforeWrapping);
        arrayCopy(oldQueue, 0, this, lengthBeforeWrapping,
                    length - lengthBeforeWrapping);
    }
};

module.exports = Queue;